Scientists of CCMB, Hyderabad in collaboration with NIO, Goa have isolated culturable bacteria from deep-sea sediments collected from the Chagos Trench in the Indian Ocean below the water depth of 5904 m. Bacteria were isolated from 50-70 cm section of a 4.6 m long sediment core. These sediments were approximately 50,000 years old. Two strains of bacteria belonging to a new species Brevibacterium oceani were described from these sediments using 16S rRNA sequencing. The almost-complete 16S rRNA gene sequences of these two strains showed 99.9% similarity among themselves. Following BLAST analysis, the two strains showed 97.9 to 98.4 % similarity to other Brevibacterium species (see Fig.). DNA-DNA dot-blot hybridization of these two strains with other known Brevibacterium species showed relatedness of only 35-41%. A DNA-DNA relatedness of 70% is used as the cut-off point for species delineation. Based on these results and differences in other phenotypic characteristics, these two strains belong to a novel species and the new species name Brevibacterium oceani was proposed. (Int. J. Systemat. Evolut. Microbiol.: 58(1); 2008; 57-60) From the same sediments, two more new strains belonging to a new species Microbacterium indicum were described. Biochemical characteristics, fatty acid profile, polar lipid contents and levels of DNA-DNA hybridization techniques were used to report this new species. 16S rRNA gene sequence similarity between the two strains was 99.7% and with other species of Microbacterium it varied from 97.2 to 97.4 %. However the two new strains exhibited 32-34% DNA-DNA relatedness to other species of Microbacterium. Therefore, based on differences observed in the phenotypic and chemotaxonomic characters, these two strains belong to a novel species of Microbacterium to which the name Microbacterium indicum was proposed. (Int. J. Systemat. Evolut. Microbiol. : 57(8); 2007; 1819-1822). These results indicate that deep-sea sediments hold a hidden wealth of microbial diversity which remains to be explored.

Neighbour-joining phylogenetic tree based on 16S rRNA gene sequences showing the position of new bacteria and closely related species of the genus Brevibacterium. Accession number given in parentheses